What Causes Humming Noise in Car When Parked?

Ever been in your garage several hours after parking your car and, all of a sudden, you hear a funny humming sound from underneath the vehicle?

There are many different types of car noise that can be caused by a variety of different things. Sometimes, it can be something as simple as a loose piece of trim or a rattling engine part. Other times, it can be something more serious, such as a problem with the brakes or suspension.

But what exactly causes humming noise in car when parked? In most cases, it could be a drive belt, air conditioning compressor, water pump, one of the components of the drive belt, or one  the idlers that keep the serpentine belt in position.

What Causes Humming Noise in Car When Parked?  

There are several potential causes of a humming noise when your car is parked, including:

1. A loose or damaged engine belt:

An engine belt, also called a drive belt, is a loop of hardwearing material that connects the engine to the various pulleys that drive the vehicle’s accessories.

The main function of an engine belt is to transfer power from the engine to these accessories. Over time, engine belts can become worn or damaged and will need to be replaced.

Replacing an engine belt is a relatively simple process that can be done at home with the help of a few tools. Before beginning, it is important to consult your vehicle’s owner’s manual to find out which type of engine belt is best for your car.

2. An overheating engine

If your car’s engine is overheating, it can make a humming noise. This is usually accompanied by other symptoms like steam coming from under the hood or the temperature gauge on the dash reading higher than normal.

3. A problem with the alternator

The charging system in most cars consists of an alternator and a voltage regulator. The alternator is a small electric motor that turns when the engine is running. Its job is to generate electricity, which it does by spinning a magnet inside a coil of wire. This process is known as electromagnetic induction.

As the alternator spins, it produces alternating current (AC). The voltage regulator controls the amount of voltage that goes to the battery and prevents the alternator from overcharging it. If it’s not working properly, it can cause a humming noise.

4. A problem with the power steering:

Power steering helps drivers steer their cars by using hydraulic fluid pressure. It is a system that makes it easier to turn the steering wheel. It’s found in either manual or automatic transmission vehicles. Most modern cars have power steering, and it is considered a standard feature.

If you notice a humming noise when you turn the wheel, it could be that the power steering fluid is low or there’s a leak in the system.In addition, the noise could be a result of the car’s evaporative emission check that happens approximately five hours after turning off the engine. It doesn’t indicate a malfunctioning engine check light since it’s a normal mechanism for the car.

Now you’re probably asking, what’s more about the evaporative emission check? Let’s see that below;

 Emission Leak Check and Enabling Conditions?

The evaporative emission leak check produces a humming sound involving pumping pressure to the gas tank to ensure its tightly sealed. The pressure system tests the tank’s filler neck, evaporative canister, and gas cap.

Given that the fuel storage system holds the pressure, the vehicle’s computer system concludes that there is no leakage and that everything is intact. Therefore, you won’t notice a check engine light despite the humming noise.

On the other hand, if the system can’t hold the pressure inside, the humming noise often occurs since the pressurizing pump has to come on every few hours. As a result, the vehicle’s computer system assumes there’s a leakage, thus turning on the check engine light.

Your take home, if the engine check light turns on in the process, first check whether the gas tank cap is airtight. This alone is a significant cause of fuel system pressure leak. However, if that isn’t the solution and the check engine light persists, that’s a direct ticket to your mechanic.

 Enabling Conditions of Evaporative Emission Leak Check? 

This process naturally happens 5 hours after your turn off your vehicle engine. Nevertheless, if the engine coolant temperature retains a temperature of 350 C (950 F) and above, the process extends from 5 to 7 hours since it depends on temperature variations.

Besides, even after the 7 hours, if the temperature remains above 350 C, the system automatically extends the time to 9.5 hours.

Other enabling conditions that trigger evaporative emission leak check include;

  • ·         An altitude of 2400 m (8000 feet) and below
  • ·         The vehicle’s battery voltage should be 10.5 v and above
  • ·         The vehicle’s ignition switch should be off.
  • ·         The engine coolant and intake air temperatures should be between 4.4 to 350 C or 400 to 950 F.  

The enabling conditions are part of the evaporative emission control system. The system detects faults within the gas tank and implements a functional and onboard refueling vapor recovery.

Another use of the evaporative emission control system is to prevent the return flow of fuel from the engine to the gas tank. It incorporates various gas tank parts such as fuel filter, sender gauge with fuel suction pump, and pressure regulatory assembly.

How To Fix Humming Noise in Car When Parked? 

To fix the humming noise problem, you first have to assess where the noise is coming from. Since the noise comes when the car is idle, you can place your vehicle in an elevated place and lie beneath as you listen to where the noise is coming from.

From that position, it’s easy to identify which side where the humming noise is coming from. If the check engine light turns on due to the noise, tighten the gas tank cap and keep observing.

Now, when underneath your car, if the noise is coming from the position just under the driver’s seat, be sure to note that it’s the effect of the fuel pump when initiating the pressure test.

However, if the humming sound comes from the rear side of your vehicle, it might be a faulty emission canister. Changing the emission canister should work if the humming or buzzing sound persists. For that, you can visit your mechanic for assistance.

How Can You Tell If The Check Detects A Faulty 

One way is when the check engine turns on. When the evaporative emission check runs and the gas tank fails to withhold the required pressure, the check engine turns on.

Nevertheless, the check engine turns on if the gas tank cap is not air-tight. As such, find out if the tank cap is closed before making further assumptions.

Of importance, note that this is not the only reason a check engine turns on. There are many other issues, only that this is one of the common ones.

Also, when the EEC keeps running every few minutes and the check engine isn’t on, there might be a slight leak around the gas tank compartments.

Although it’s not a cause of alarm, have it checked when you drive to your mechanics.   

On Humming Noise in Car When Parked

In conclusion, if you’ve frequently experienced the humming noise several hours after turning off your vehicle noise, don’t fume thinking it’s yet another visit to the mechanic. It might be a quick fix issue that takes you a few minutes.

Therefore, assess the vehicle keenly and establish where the noise is coming from. From there, the next step is identifying whether it’s the normal evaporative emission check or another issue within your car.

Take the necessary precautions like tightening the gas tank cap, and if the noise persists, visit your mechanic for diagnosis. 

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